Environment and health: New insights into spread of infectious diseases
Scientists have offered the world another good reason to protect the environment. They have identified a loathsome catalogue of infectious diseases that have revived and thrived in places where natural habitats are altered or degraded by loggers, road and dam builders and urban encroachment.
The Story
The impact of human activity on the environment takes numerous forms, many
of them well publicized, but experts seem to have now identified another
side effect of this interaction that has direct implications for people’s
health.
The United Nations Environment Programme (UNEP) cautions that the loss of forests,
road and dam building, the spread of cities, the clearing of natural
habitats for agriculture and mining and the pollution of coastal waters are
promoting conditions under which new and old pathogens -- bacteria, viruses
and micro-organisms causing diseases -- can thrive. UNEP notes that intact
habitats and landscapes tend to keep infectious agents in check, whereas
damaged, altered and degraded ones shift the natural balance, thereby
triggering the spread to people of new and existing diseases. UNEP also
points to possible linkages with climate change which can alter temperatures
to the advantage of carriers such as mosquitoes or stress the environment
and alter habitats to such a degree that people migrate as “environmental
refugees”.
The World Health Organization has noted the appearance of at least 30 new
diseases in the last two decades “to threaten the health of hundreds of
millions of people.”
The Context
- A team from Johns Hopkins University in the US found that even a 1
per cent increase in deforestation in Peru increases the number of
malaria-bearing mosquitoes by 8 per cent. The study showed that the insects
"ran wild" after 30 to 40 per cent of the forest was destroyed. Mosquitoes
can transmit more than 100 viruses known to infect humans, including:
dengue fever, yellow fever, and sometimes fatal encephalitis and
haemorrhagic fever.
- Rapid, unplanned urbanization has been identified as the major driving
force behind an explosion of dengue fever, from less than 1,000 cases per
year in the 1950s to a situation in which some 2.5 million people are at
risk today.
- The highly pathogenic Nipah virus, which was until recently found only
in Asian fruit bats in Indonesia and Malaysia has been tied to forest loss.
UNEP's Global Environment Outlook report observes that a combination of forest
fires in Sumatra and deforestation in Malaysia forced the bats into closer
contact with domestic pigs which gave the virus its chance to spread to pig
farmers in the late 1990s.
- A study from gem-mining areas in Sri Lanka has shown that the shallow
pits left behind by the miners are ideal breeding grounds for mosquitoes and
epicentres of malaria.
- In the United States, cases of the tick-borne Lyme disease in New York
and Connecticut have surged as humans have moved into forested areas where
tick-carrying deer thrive.
For further information
United Nations Environment Programme (UNEP):
Eric Falt, Spokesman/Director, Division of Communications and Public
Information, Tel: +254 20 623292, E-mail:
eric.falt@unep.org;
Nick Nuttall, Head of Media, Tel: +254 20 623084, E-mail:
nick.nuttall@unep.org;
Marion Cheatle, Officer in Charge, Division of Early Warning and Assessment,
Tel: +254 20 623520, E-mail:
marion.cheatle@unep.org
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